The cervical portion of the vertebral column creates the skeletal background. It is composed of seven cervical vertebrae, with a characteristic anterior convex curvature. Vertebrae C3 through C6 are considered to be typical cervical vertebrae. Vertebrae C1, C2, and C7 are atypical cervical vertebrae. C1 (atlas) has no body. C2 (axis) has incorporated the body of C1 in its structure. The combination of the two bodies results in a tooth-like projection called the odontoid process, or dens epistrophe.

This provides an axis of rotation for the skull on the atlas. C7 has a large transverse mass with a primitive foramen and a prominent spinous process (vertebra prominens). The typical cervical vertebrae have a bifid spinous process and a distinct foramen in the transverse mass. There are anterior and posterior tubercles related to the transverse mass. The first rib must be included in the skeletal background. Many of the neck structures are attached to, or pass over, the first rib. The superior surface of the first rib is flattened. This will avoid trauma to the neurovascular structures that travel over it. Midway between the vertebral and the sternal ends of this rib is the scalene tubercle, point of insertion of the anterior scalene muscle. A vascular sulcus is found on both sides of the scalene tubercle. The anterior sulcus provides passage for the subclavian vein. The subclavian artery passes over the posterior sulcus. The anterior scalene muscle attaches to the first rib between the subclavian vessels. The middle scalene muscle attaches to the first rib posterior to the groove for the subclavian artery. Therefore, the subclavian artery passes through the scalene triangle that is created by the anterior and middle scalene muscles. This area is referred to as the root of the neck. It will be described in more detail later in this chapter.

The ligamentous background includes supporting structures for the atlanto-occipital and atlantoaxial joints. The anterior longitudinal ligament is found on the anterior aspect of the vertebral bodies. It extends
from the atlas down to the upper sacral segment. It is attached to the intervertebral disc and that portion of the vertebral body lying just superior and inferior to the disc. The nuchal ligament covers the spinous processes of all the cervical vertebrae.

The muscular background includes muscles that are attached to the anterior aspect of the vertebra (anterior vertebral) and muscles that are attached to the lateral mass of the vertebra (lateral vertebral). Both of these groups are combined and are referred to as prevertebral muscles. The longus coli and longus capitis muscles are anterior to the vertebral column. The longus coli is a complex muscle that is attached inferiorly to the upper thoracic portion of the anterior longitudinal ligament. These lower fibers pass superolaterally and attach to the transverse masses of the typical cervical vertebrae. Fibers of this same muscle then pass superomedially and attach to the anterior portion of the arch of the atlas. There are vertical fibers of this same muscle that lie between the two oblique portions laterally and the anterior longitudinal ligament medially.

The longus capitis muscle lies anterior to the superomedial fibers of the longus coli muscle. It passes from the base of the skull to the tubercles of the typical cervical vertebrae. The muscles that are lateral vertebral in position are the levator scapula, middle, and anterior scalene muscles. The levator scapula muscle is the most posterior of this lateral group. It arises from the posterior tubercles of the transverse masses of the first four cervical vertebrae, descends, and attaches to the superior portion of the vertebral border of the scapula. The middle scalene muscle is on a more anterior plane (Fig. 1).

The middle scalene muscle may be attached to the posterior tubercles of all cervical vertebrae. It descends and affixes to the superior flattened surface of the first rib, posterior to the groove for the subclavian artery. A few muscle fibers extend down to the second rib and create the posterior scalene muscle. The most anterior of the lateral vertebral muscles is the anterior scalene (Fig. 1). It arises from the anterior tubercles of the transverse masses of the typical cervical vertebrae and attaches below to the scalene tubercle of the first rib. It is in the same frontal plane as the longus capitis muscle. The anterior vertebral muscles will flex the cervical spine. The lateral vertebral muscles will cause lateral bending of the same area. Motor innervation is provided by ventral rami of cervical nerves.

The nerve layer should now be inserted. The nerves and the muscles are intimately related, so that the term “neuromuscular layer” is appropriate. The cervical and brachial plexuses and the cervical sympathetic chains are now encountered as we continue the reconstruction of the neck.

The cervical sympathetic chain consists of three ganglia with connecting branches. The superior ganglion is the largest, and it is found on the transverse mass of the second and third cervical vertebrae. It is >1 in. long and lies on the longus capitis muscle, posterior to the carotid sheath. The middle cervical ganglion is the smallest and lies on the transverse mass of the sixth cervical vertebra. The inferior cervical ganglion is related to the vertebral end of the first rib and the transverse mass of the seventh cervical vertebra. It frequently joins with the first thoracic ganglion to form a dumbbell-shaped structure called the cervicothoracic, or stellate, ganglion. Stellate refers to the star-like appearance created by the multiple branches that are emitted. It is posterior to the vertebral artery. At times, branches from the middle cervical ganglion will form a loop around the subclavian artery before entering the inferior ganglion. This is referred to as the ansa subclavia.

The cervical plexus is formed by the ventral rami of the first four cervical nerves. These nerves connect to each other by forming loops that lie in the interval between the levator scapula, or the middle scalene, muscle posteriorly, and the longus capitis or its inferior continuation, the anterior scalene muscle, anteriorly (Fig. 2).

Each of the first four cervical ventral rami receives a branch from the superior cervical ganglion. The cervical nerves lie within the prevertebral fascia. The cervical plexus provides muscular and cutaneous innervation. There are cutaneous branches from a superficial cervical plexus and muscular branches from a deep cervical plexus. The cutaneous branches will be described with the posterior triangle. Muscular branches innervate the prevertebral muscles. In addition, a branch from C1 travels with the hypoglossal nerve and gives rise to the superior limb (descending hypoglossal nerve) of the ansa cervicalis. Branches from C2 and C3 will form the inferior limb (descending cervical nerve). The two limbs unite and form the ansa cervicalis. This nerve loop is on the anterior aspect of the carotid sheath, in the cricoid plane. Branches arise from the ansa cervicalis that provide motor innervation to the strap muscles in the muscular triangle. Other branches of C1,
traveling with the hypoglossal nerve, provide motor innervation to the thyrohyoid and geniohyoid muscles. A branch from C4 descends on the anterior surface of the anterior scalene muscle, within the prevertebral fascia. It is the phrenic nerve and it may receive branches from C3 and C5. It is, at first, seen on the lateral aspect of the anterior scalene muscle, but as it descends it passes obliquely across the anterior surface of the muscle and reaches its medial edge in the root of the neck. It then passes anterior to the subclavian artery and courses medial to the internal mammary artery before entering the thorax. It provides sensory and motor innervation to the respiratory diaphragm (Fig. 2). There are some proprioceptive branches arising from the cervical plexus that pass to the sternocleidomastoid and trapezius muscles.

As we pass inferiorly in the cervical region, the nerves now encountered will consist of the roots and trunks of the brachial plexus. The brachial plexus is created by the ventral rami of C5 through T1. These roots will form three trunks. C5 and C6 join to form the upper trunk. The C7 root will become the middle trunk, and roots C8 and T1 will merge and form the lower trunk. These roots and trunks pass between the middle and the anterior scalene muscles. The lower trunk is draped over the first rib immediately posterior to the subclavian artery (Fig. 2).

The subclavian vein, unlike the accompanying artery, does not pass between the scalene muscles. It passes anterior to the anterior scalene muscle. Enclosing the skeletal background and the neuromuscular layer is the prevertebral portion of the deep cervical fascia. The neurovascular structures will pierce the deep cervical fascia and drag a portion of it along with them, creating the axillary, or cervicoaxillary, sheath.

The cervical fascia is composed of superficial and deep layers. The superficial fascia is not well developed and not easy to find. It consists of fat and some connective tissue. The platysma muscle is in the superficial fascia. It arises inferiorly from the fascia of the pectoralis major muscle and its fibers converge as they ascend to their insertion in the inferior part of the mandibular region. Some of the muscle fibers ascend and mix with the intrinsic depressor muscles of the lips. The cutaneous nerves and the superficial veins course below this muscle of facial expression. The cervical branch of the facial nerve innervates this muscle.

The deep cervical fascia consists of several layers. The superficial, or investing, layer of the deep cervical fascia splits to invest the trapezius and sternocleidomastoid muscles and the submandibular and parotid glands. It creates a complete tube that surrounds the neck. The deep layer of the deep cervical fascia, or prevertebral fascia, encloses the vertebral column and the attached erector spinae and prevertebral muscles and proximal portions of the cervical and brachial plexuses. It creates a complete tube.

The pretracheal fascia creates a tube that encircles the pharynx and esophagus, larynx and trachea, and the thyroid and parathyroid glands. The buccopharyngeal fascia is the posterior extension of the pretracheal fascia that covers the constrictor muscles of the pharynx. It is in contact with the anterior, or prevertebral, portion of the prevertebral fascia. This potential space between the prevertebral and the buccopharyngeal fascia layers extends from the neck down to the mediastinum. This retropharyngeal space can serve as a pathway for the spread of an infection from the neck to the thorax. The middle cervical fascia extends from the hyoid bone to the sternum. It encompasses all the strap muscles. This fascia layer extends laterally to the omohyoid muscle and therefore is only related to the muscular and subclavian triangles.

The carotid sheath is a protective, tubular fascial sheath found between the base of the skull and the root of the neck. It receives tissue contributions from all layers of the deep cervical fascia and encloses the common carotid and internal jugular vascular conduits and vagus nerve. After the bifurcation of the common carotid artery, the internal carotid branch will assume its position in the sheath. The vein is anterolateral to the artery, except at the base of the skull, where the vein lies posterior to the artery. The vagus nerve is between, and slightly posterior to, the blood vessels. The ansa cervicalis is on the anterior surface of the sheath in the cricoid plane. The sympathetic chain is in contact with the posterior surface of the sheath.

The root of the neck compression syndromes include the following:

If the space between the first rib and the clavicle should be decreased, there could be compression of the neurovascular structures traversing this area (Fig. 5). The subclavian vein is the most medial of the neurovascular structures passing through the costoclavicular space. The vein is in the narrowest portion of this space, and if additional narrowing occurs, venous outflow from the upper extremity may be impaired.

A cervical rib may present itself in several ways. It is frequently bilateral. It is an extension of the transverse mass of the seventh cervical vertebra and it may be a complete rib that articulates with the sternum. At times, it may fuse with the first rib or present as a fibrous band that attaches to the first rib. In some patients, it may have an anterior end that is free. The subclavian vessels and the brachial plexus, especially the lower trunk, will be affected adversely when they try to pass over this additional obstacle.

The anterior scalene compression syndrome results from spasm, or hypertrophy, of the anterior scalene muscle, with resultant constriction of the neurovascular elements as they pass through the scalene triangle. If the clinician treats this condition by transecting the anterior scalene muscle near its insertion, the position of the phrenic nerve and the subclavian vein, passing anterior to the muscle, must be remembered.

The term “thoracic outlet compression syndrome” is frequently used when defining some clinical conditions encountered in the root of the neck. Thoracic outlet is a misnomer when used to identify the clinical problems in this area. The true anatomical thoracic outlet is the area related to the respiratory diaphragm. Correct terms for these conditions would include superior thoracic aperture compression syndrome or cervicoaxillary compression syndrome.

All of these compression syndromes can result in neurologic deficits and/or arterial and venous circulatory problems in the upper extremity.

The sternocleidomastoid and trapezius muscles divide the neck into anterior and posterior triangles (Fig. 6; also see Fig. 13). The boundaries of the posterior triangle are the trapezius muscle posteriorly and the sternocleidomastoid muscle anteriorly. The middle third of the clavicle creates the inferior limit, and the apex of the triangle extends to the superior nuchal line. The triangle is spiral in shape. The inferior portion is anterior in the neck, but the apex is posterior. The anterior triangle includes the area between the anterior edges of the sternocleidomastoid muscles. The superior limit is the mandible and a line drawn from the angle of the mandible to the tip of the mastoid process. Two double-bellied muscles, omohyoid and digastric, subdivide the triangles. The inferior belly of the omohyoid muscle attaches to the superior transverse scapular ligament and a portion of the adjacent superior edge of the scapula. It passes superior to the clavicle and enters the lower portion of the posterior triangle. The intermediate tendon is in the cricoid plane, anterior to the carotid sheath, and is angulated by a fascial sling attached to the clavicle and the manubrium. The superior belly ascends to the hyoid bone.

The posterior triangle now consists of the large occipital and the smaller subclavian triangles. The digastric is the other double-bellied muscle that creates subdivisions of the anterior triangle. The posterior belly attaches just medial to the mastoid process. The intermediate tendon is tethered to the hyoid bone by a fold of deep cervical fascia. The stylohyoid muscle arises from the styloid process of the temporal bone and is in intimate contact with the anterior surface of the posterior belly of the digastric muscle. The tendon of insertion of the stylohyoid muscle to the hyoid bone is split and allows for passage of the intermediate tendon of the digastric muscle. The anterior triangle includes the submandibular and carotid triangles. They are separated from each other by median submental and muscular triangles.

The hyoid bone is a central structure in the neck. It is directly or indirectly attached to most of the muscular and membranous entities in the anterior triangle and in the floor of the mouth. If one considers the hyoid bone and the attached posterior belly of the digastric muscle, it is possible to divide the anterior triangle into suprahyoid and infrahyoid portions. The submandibular, or digastric triangles, and the submental triangle, are suprahyoid entities and are related to the floor of the mouth. They have been discussed in another chapter. The carotid and the muscular triangles are found in the infrahyoid portion of the anterior triangle.

The muscular boundaries of the carotid triangle are the sternocleidomastoid muscle posteriorly, the posterior belly of the digastric muscle anterosuperiorly, and the superior belly of the omohyoid muscle anteroinferiorly (Fig. 7). The greater horn of the hyoid bone is part of the anterior and superior segment of the floor of this triangle. The hyoglossus and thyrohyoid muscles are attached to this portion of the hyoid bone, and are part of the anterior portion of the muscular floor. A small portion of the thyrohyoid membrane is found just behind the thyrohyoid muscle and makes up a small area of the floor. The middle and inferior pharyngeal constrictor muscles create the posterior section of the muscular floor of the carotid triangle. The longus capitis, a prevertebral muscle, also contributes to the posterior portion of the muscular floor of this triangle. The pretracheal layer of the deep cervical fascia creates the fascial carpet. The investing layer of the deep fascia creates a fascial roof.